Proper adhesion of soft tissue to orthopaedic implants is important but has proven difficult to achieve. For example if the implant surface to which tissue adherence is desired is smooth, tissue cannot easily adhere to the implant and the body forms a tissue capsule around the implant, sealing it off from the rest of the body. This impairs the implant's function. Since the implant constantly moves relative to the tissue, resulting friction causes inflammation and creates a steadily growing capsule of dead tissue. Accordingly, implant surfaces to which tissue adherence is desired have been textured, but too great a degree of surface roughness can permit connective tissue and bone to grow into the fissures. The implant essentially grows into the body and removal of the implant becomes almost impossible, and if possible results in major bone loss.
Shot peening has been used to increase strength and wear resistance of orthopaedic implants, as disclosed in U.S. Pat. No. 5,704,239. Shot peening to increase strength uses shot media of a size and applied at an intensity sufficient to compress the layer just under the surface to thereby increase strength. Shot having a diameter of 0.0011″–0.0023″ would typically be used (identified by industry standard S110–S130 shot).